DESCRIPTION OF THE NEW LABORATORIES OF THE
DEPARTMENT OF NAVAL ARCHITECTURE, UNIVERSITY
OF TECHNOLOGY, DELFT, H O L L A N D
Part /. The laboratory for Ship Structure Research
byProf. Ir. H. E. J A E G E R a n d ir. J . C h . D E D O E S
Part II. The Shipbuilding Laboratory
by Ir. J . GERRITSMA
Reprinted from
INTERNATIONAL SHIPBUILDING PROGRESS ROTTERDAM
A MODERN LABORATORY FOR TESTS A N D RESEARCH
O N SHIPS' STRUCTURES
by
Prof. Ir. H. E. JAEGER*) and Ir. J . C . DE D O E S * * )
Summary
A description of the Laboratory for Ship Structure Research at the University of Technology in Delft,
Netherlands, is given. The aim and the need for ships' structure research is discussed; Special attention is drawn to the great facilities for research available in this laboratory.
1. Introduction
S h i p b u i l d i n g is f o r the N e t h e r l a n d s a v e r y v i t a l i n d u s t r y . W h e n a f t e r W o r l d - w a r I I the necessity f o r research i n n a v a l c o n s t r u c t i o n was f e l t every-w h e r e i t every-was e v i d e n t t h a t the N e t h e r l a n d s every-w a n t e d to take u p t h e i r share i n the d e v e l o p m e n t o f m o d e r n s h i p b u i l d i n g , I t was clear t h a t f u r t h e r development, or even the maintenance o f the level o f m o d e r n D u t c h s h i p b u i l d i n g was o n l y possible as long as f u n d a m e n t a l as w e l l as p r a c t i c a l research was u n d e r t a k e n o n a scale u n k n o w n t i l l 1940.
T h e N e t h e r l a n d s S h i p b u i l d i n g Research Associ-a t i o n cAssoci-ame i n t o b e i n g , w h i c h correlAssoci-ated Associ-as f Associ-a r Associ-as possible this research i n s h i p b u i l d i n g i n the N e t h e r -lands. B u t this association d i d n o t o w n laboratories and the yards also had v e r y l i t t l e e q u i p m e n t f o r u n d e r t a k i n g f u n d a m e n t a l research. A p a r t f r o m h y d r o d y n a m i c research i n the N e t h e r l a n d s Ship M o d e l Basin, no. research i n s h i p b u i l d i n g was carried o u t i n this c o u n t r y .
T h e r e f o r e w h e n an extension o f the facilities f o r s h i p b u i l d i n g was made at the U n i v e r s i t y o f T e c h -n o l o g y i -n D e l f t , the idea was co-nceived o f i -n s t a l l i -n g a l a b o r a t o r y f o r t e s t i n g ships' structures, a b r a n c h o f research undeveloped u n t i l then.
This b r a t i c h is v e r y necessary. I m m e d i a t e l y a f t e r
the w a r i t became k n o w n t h a t m a n y d i f f i c u l t i e s had been experienced d u r i n g the w a r w i t h a l l -w e l d e d ships. T h e t e c h n i c a l reports f r o m the U . S . A . and G r e a t B r i t a i n made i t clear t h a t the results o f investigations o n b r i t t l e f r a c t u r e o f the m a t e r i a l , were largely i n f l u e n c e d b y the size o f the s t r i i c t u r e and the w a y i n w h i c h i t was made, and t h a t these circumstances were o f great i m p o r t a n c e w i t h regard to the b e h a v i o u r o f this s t r u c t u r e as a p a r t o f the ship.
M o r e o v e r n e w p r o b l e m s came i n t o being and w i t h a l i t t l e f o r e s i g h t , special facilities c o u l d be designed t o ensure adequate l a b o r a t o r y technique i n the near f u t i i r e . Problems such as the behaviour
' ) P r o f e s s o r o f N a v a l C o n s t r u c t i o n at t h e U n i v e r s i t y o f T e c h n o l o g y o f D e l f t , D i r e c t o r o f R e s e a r c h o f t h e N e t h e r l a n d s ' S h i p -b u i l d i n g R e s e a r c h A s s o c i a t i o n a n d o f t h e L a -b o r a t o r y f o r S h i p ' S t r u c t u r e R e s e a r c h at t h e U n i v e r s i t y , * * ) P r i n c i p a l s c i e n t i f i c o f f i c e r o f t h e l a b o r a t o r y f o r S h i p S t r u c t u r e R e s e a r c h a t the U n i v e r s i t y o f T e c h n o l o g y i n D e l f t .
o f c o r r u g a t e d bulkheads, the behaviour o f large welded c o n s t r u c t i o n s as e m p l o y e d i n supertankers, the transmission o f forces b y means o f brackets^ the d i s t r i b u t i o n o f forces i n large superstructures etc. etc. were asking f o r a s o l u t i o n .
M a n y problems as f o r instance research o n b r i t t l e f r a c t u r e and the behaviour o f structures i n the plastic range a l l need f u l l scale experiments. T h e o r e t i c a l considerations alone are n o t s u f f i c i e n t and they become more valuable w h e n combined w i t h measurements i n laboratories as w e l l as o n ships.
I t is clear, t h a t u n d e r e x i s t i n g circumstances the best w a y t o c a r r y o u t tests o n the s t r e n g t h o f ships is t o have t h e o r e t i c a l l y t r a i n e d m e n w o r k i n g o n this j o b so t h a t t h e y m a y learn at the same t i m e as m u c h as possible f r o m i t . . T h e r e f o r e i t was evident t h a t this l a b o r a t o r y had t o have c o m b i n e d w i t h i t the t r a i n i n g o f o u r y o u n g n a v a l architects and hence this p r o p o s i t i o n was s u b m i t t e d b y the f i r s t a u t h o r to the D u t c h G o v e r n m e n t , as the U n i v e r s i t y o f T e c h n o l o g y i n D e l f t is a state i n s t i t u t i o n . H i s p o i n t o f v i e w was shared b y the M i n i s t e r o f E d u c a t i o n and the l a b o r a t o r y r e s u l t i n g f r o m the above m e n t i o n e d considerations is described hereafter. 2. Some fundameittal considerations on
strength-research
S t r e n g t h research o n ships m a y be d i v i d e d i n t o t w o parts:
1. T h e i n v e s t i g a t i o n i n t o the loads a c t i n g on the ship due t o sea waves and t o the d i s t r i b u t i o n o f w e i g h t .
2. T h e d e t e r m i n a t i o n o f the most suitable c o n -structions t o resist loads d e f i n e d beforehand. T h e f i r s t named investigations require collabo-r a t i o n w i t h the D e l f t Ship M o d e l Basin. T h e behaviour o f ships i n a seaway has to be investigated f i r s t and the t o w i n g basin has already the necessary electronic apparatus to measure the movements o f ship models i n an a r t i f i c i a l seaway. A description o f the D e l f t S h i p b u i l d i n g Laiboratory is g i v e n i n P a r t . I L
I n D e l f t there is the possibility o f invest:igating the loads due t o a seaway o n a plastic scale m o d e l
F i g . ) . C r o s s section of Ihe Lahoniiory
o f a ship, where the forces, moments and stresses w i l l be measured i n a specially designed w a y .
T h e investigations m e n t i o n e d i n the second place embrace a v e r y extensive f i e l d o f research. L o n g i -t u d i n a l a n d -transverse s -t r e n g -t h o f ships, local
s t r e n g t h , properties o f materials, c o n n e c t i o n o f s t r u c t u r a l parts as already i n d i c a t e d i n § 1 give a great m a n y possibilities o f i n v e s t i g a t i o n , w h i c h f o r a great p a r t w i l l have t o be done o n the f u l l scale to a v o i d the i n f l u e n c e o f scale e f f e c t . I t is f o r
instance impossible to determine the i n f l u e n c e o f i n t e r n a l stresses due t o w e l d i n g on scale models. T h i s means t h a t the c o m p l i c a t e d welded structures o f m o d e r n s h i p b u i l d i n g have to be tested on the actual size and b u i l t o f the actual m a t e r i a l , even i f such a s t r u c t u r e is o n l y a small p a r t o f the ship. O n l y where drawbacks due to scale e f f e c t do n o t exist, w i l l i t be advantageous t o resort t o scale models and t h e r e f o r e an extensive arrangement f o r s t r e n g t h - m o d e l - t e s t i n g is available i n the laboratory and a l l kinds o f electrical and electronical measuring equipments can be used.
3. General description of the laboratory
F i g . 1, 2 and 3 give an i n d i c a t i o n o f the general l a y - o u t o f the new l a b o r a t o r y i n the d e p a r t m e n t o f N a v a l A r c h i t e c t u r e at the U n i v e r s i t y o f T e c h -n o l o g y i -n D e l f t . I t is a p a r t o f the b i g b u i l d i -n g s h o w n i n F i g . 4 where i t is i n d i c a t e d b y " A " . T h e p r i n c i p a l p a r t consists o f a h a l l w i t h an area o f 28,6 m X 13,2 m (95'-0" X 43'-4") and a h e i g h t o f 8,50 m ( 2 8 ' - 0 " ) . T o the l e f t o f this h a l l t w o tiers o f rooms f o r investigators and other personal o f the l a b o r a t o r y are b u i l t . A t B ( F i g . 1) a p i t is b u i l t , i n w h i c h a s t r u c t u r e consisting o f f o u r d i f f e r e n t bulkheads, f o r m i n g a t a n k , m a y be
F ! g . 4 . The iieif Biiililiiig for Meclianical Etigiiieeriiig and Nai'al Conslrucliou J LabarjitaT-y—lorSbiti-SLrMclure Kesear^ii^—b,—Ton-'iiifi Ttnik
Phoro K.L.M.
6
Fig. S. Geiienil arrange men I 5(10 ji iiiachhic
erected. B y means o f this t a n k , b u l k h e a d i n v e s t i -gations w i l l be made, w h i c h w i l l be described at a f u t u r e date.
T h i s .pit together w i t h the 500 tons tensile-, compression t e s t i n g machine ( A ) f i l l s the greater p a r t o f the f l o o r space o f the h a l l . F a c i n g the large testing m a c h i n e are a 6 - t o n ( C ) and a 100 tons f a t i g u e t e s t i n g machine ( E ) whereas beneath these m a c h i n é s s u f f i c i e n t floor-space is available f o r scale-model-tests. O n the g r o u n d f l o o r are installed • a store r o o m f o r i n s t r u m e n t s and a measuring
r o o m . O n the gallery along the h a l l are the room's f o r the s t a f f and the t e c h n i c a l personel and a d a r k room. The.necessary w o r k shops are situated i n the p a r t o f the b u i l d i n g , w h i c h contains the t o w i n g -basin.
4. Description of the more important testing
machines
a. T h e 500 t o n tensile-compression t e s t i n g machine
T h i s machine is o f the h o r i z o n t a l t y p e and is made as large as possible i n v i e w o f the large test-pieces t o be tested. T h e design was b y A l f r e d J . A m s l e r o f S w i t z e r l a n d f r O m a s p e c i f i c a t i o n o f the U n i v e r s i t y . T h i s f i r m also m a n u f a c t u r e d the h y -drauHc e q u i p m e n t . T h e f r a m e was c o n s t r u c t e d at the. R o t t e r d a m D r y d o c k C o m p a n y . T h e end c o n -nections o f the test pieces can be absolutely r i g i d or c o m p l e t e l y f r e e . W i t h 500 tons load an eccen-t r i c i eccen-t y o f 2.5 c m ( l O " ) i n eccen-the h o r i z o n eccen-t a l d i r e c eccen-t i o n
and 10 c m ( 4 " ) i n the v e r t i c a l d i r e c t i o n is possible. T h i s means, t h a t i n a d d i t i o n t o a tensile or a compressive f o r c e the a p p l i c a t i o n o f a l i m i t e d b e n d i n g m o m e n t is possible.
Fig. 5, 6 a n d 7 give a general idea o f the m a c h i n e . I t rests o n a v e r y heavy concrete f o u n d a t i o n and consists o f a steel f r a m e , f o r m e d b y t w o l o n g i t u d i n a l beams 21,65 m l o n g ( 7 l ' 0 " ) , c o u p l e d t o -gether at t h e i r ends. E a c h beam' consists o f a D I N
40 I beam w i t h t w o heavy flanges 530 X 60 m m
X 2 % " ) w e l d e d together. T h e sectional area
is so large t h a t w i t h 500 tons load the m a x i m u m stress is o n l y 260 K G / c m ^ (3720 I b s / s q . i n c h ) , the e l o n g a t i o n b e i n g o n l y 0,23 c m ( 0 . 1 " ) .
T h e heavy flanges f o r m the rails f o r the t w o crossheads, o f w h i c h one is f i x e d and the other m o v a b l e a l o n g the beams. T h e f i x e d crosshead can be placed at any desired place, dependent o n the l e n g t h o f the testpiece. So f o r every testpiece the f u l l stroke o f the rams is available.
T h e r a m crosshead is m a n i p u l a t e d b y 8 h y d r a u l i c rams, each g i v i n g a f o r c e o f 12 5 tons. F o u r o f these rams w o r k i n the tensile d i r e c t i o n and f o u r i n the c o m p ression-direction.
E a c h crosshead is resting o n a k i n d o f carriage
i n each beam. These carriages have roller-bearings. F i g . 8 gives a view o f such a carriage before m o u n t i n g o n the crosshead. I n the m i d d l e is the bearing i n w h i c h the r o u n d e d pinhead o f the cross-head is resting.
T h e crossheads are heavily welded box-shaped structures, w h i c h give the lightest w e i g h t f o r the greatest s t r e n g t h . T h e w e i g h t o f each crosshead is
23 tons; the c o n s t r u c t i o n is g i v e n i n F i g . 9. T h e
crossheads have m a c h i n e d pressure-faces, w h i c h , however, are n o t s t r o n g enough t o s u p p o r t a c o n -centrated load o f 500 tons. I f this is desired a special set o f pressure platens is inserted between the faces t o d i s t r i b u t e the f o r c e over a larger area.
F i g . 8. Cnrringe for Ihe xiiiiliiig
of Ihe fixe:! crosshead before
imntttl irlfi
Fig. 12. Regulating valves for the steering oj the ram crosshead
For the c o n n e c t i o n o f these platens, the crossheads have w e l d e d t h r o u g h tubes c o n n e c t i n g the f o r e and a f t faces.
T h e h o r i z o n t a l shearing forces are t r a n s m i t t e d to the beams at the positions o f the ram-crosshead and the f i x e d crosshead. T h e f i x e d crosshead w i l l t r a n s m i t these h o r i z o n t a l forces d i r e c t l y to the f o u n d a t i o n b y means o f v e r t i c a l s t o w i n g beams, w h i c h are i n d i c a t e d i n F i g . 5 and 6. T h e b i g l o n g i -t u d i n a l beams are s -t r o n g l y f i x e d -t o -the f o u n d a -t i o n i n the axial d i r e c t i o n o n l y at the end where the p u m p r o o m is s i t u a t e d . I n the axial d i r e c t i o n , these beams are absolutely f r e e t o elongate. T h e shearing forces at t h a t end are t o be c a r r i e d d i r e c t l y b y the f o u n d a t i o n t o p r e v e n t b u c k l i n g o f the l o n g i t u d i n a l beams.
I n the v e r t i c a l d i r e c t i o n the beams are connected to the f o u n d a t i o n b y means o f t r a c t i o n - b a r s and plates. T h e beams are absolutely h o r i z o n t a l and the m a x i m u m d e v i a t i o n f r o m the h o r i z o n t a l p o s i t i o n is less t h a n 0,1 m m ('/sBoth o f an i n c h ) .
T h e f i x e d crosshead is k e p t i n place b y means o f a s u p p o r t , w h i c h is f i x e d t o the beams b y large steel pins. Holes are made i n the beams at a p i t c h o f 75 c m ( 3 0 " ) , b u t nevertheless the f i x e d cross-head can be placed at a n y desired distance f r o m the movable one b y means o f f o u r rods. I n this w a y any o b j e c t m a y be tested between these t w o cross-heads w i t h the f u l l stroke o f JO c m ( 2 0 " ) . These supports are i d e n t i c a l t o the f i x e d ones, w h i c h sup-p o r t the 8 h y d r a u l i c rams as can be seen i n F i g .
J. T h e c o n s t r u c t i o n o f the rams and the supports
is g i v e n i n F i g . 10.
T h e concrete f o u n d a t i o n is s h o w n i n F i g . 11. I t is absolutely f r e e f r o m the b u i l d i n g itself. W h e n the test-pieces are tested to f a i l u r e e.g., enormous quantities o f energy w i l l be released at the m o m e n t o f collapse. T h e r e f o r e the reaction-forces are taken over b y the v e r y h e a v i l y r e i n f o r c e d concrete f o u n d a t i o n , w h i c h has the f o r m o f a basin. I t m a y be desirable to s u p p o r t v e r y l o n g test pieces and i n this case the basin can be f i l l e d w i t h water. T h i s makes i t possible to make use o f an elastic f o u n d a t i o n b y means o f pontoons.
T h e basin has dimensions o f 21,65 m X 6,90 m X X 3,13 m ( 7 r - 0 " X 22'-8" X 1 0 ' - 4 " ) and the b o t t o m thickness is 1,00 m ( 3 ' - 3 " ) . T h e free w i d t h between the sides o f the basin is 5,20 m ( 1 7 ' - ! " )
m
and the basin is constructed below groundleVel, so that the tops o f the vertical walls are o n l y 45 c m ( l ' - 6 " ) h i g h . T h e test space is t h e r e f o r e v e r y large and the m a x i m u m dimensions o f the test pieces are
12,50 m X 5,00 m (41'^0" X 1 6 ' - 5 " ) .
T h e r i g h t - e n d o f the basin is separated f r o m the p u m p - r o o m b y a concrete w a l l . T h e supports o f the crossheads are placed against the concrete side walls o f the basin b y means o f shock-absorbersj as s h o w n i n F i g . 10.
A p a r t f r o m the h o r i z o n t a l compression or t r a c t i o n a v e r t i c a l system o f lateral f o r c e s u p to
100 tons m a y be applied.
T h é m a i n p a r t o f the .machine is the h y d r a u l i c i n s t a l l a t i o n . A s already stated a special f e a t u r e o f the machine is the possibility o f a l t e r i n g the end conditions o f the test piece. I n other w o r d s i t w i l l be possible t o test a c o n s t r u c t i o n w i t h r i g i d or t o t a l l y f r e e end c o n d i t i o n s . I f the end c o n n e c t i o n is to be considered as absolutely f r e e i t is essential to give the r a m crosshead the r e q u i r e d f r e e d o m o f m o v e m e n t . T h e r e f o r e the test load is applied b y f o u r ramsj t h a t are h y d r a u l i c a l l y connected. I f f i x e d end c o n d i t i o n s are desired and the crosshead gets a m o v e m e n t w h i c h is n o t absolutely parallel to its Original p o s i t i o n , the m o v a b l e crosshead w i l l r e c t i f y , its d i r e c t i o n a u t o m a t i c a l l y , b y means o f f o u r l i t t l e axiometer'-valves (see F i g . 1 2 ) . E v e r y ram. has Its o w n o i l s u p p l y via these valves.
T h e d i a g r a m o f the h y d r a u l i c system is given i n F i g . 13. T h e r e are f i v e d i f f e r e n t systems v i z . :
1. T h e low-pressure servo system. 2. T h e high-pressure system.
3. T h e l o w pressure s e t t i n g and r e t u r n system. 4. T h e m e a s u r i n g system.
5. T h e e q u i l i b r i u m - s y s t e m f o r the r a m
cross-head'.
T h i s e q u i l i b r i u m system neutralises a possible m o m e n t , due t o the w e i g h t o f the r a m crosshead or the test piece. T w o s m a l l h y d r a u l i c cyUndei-s just balance the w e i g h t m o m e n t o f these parts;.
I n the d i a g r a m are s h o w n the 8 h i g h - p r e s s u r e rams ( A ) , the p i l o t c y l i n d e r w i t h a x i o m e t e r - d e v i c e ( C ) , the e q u i l i b r i u m c y l i n d e r s ( D ) the c o n t r o l panel ( E ) the p e n d u l u m - m a n o m e t e r ( F ) and the r e g u l a t i n g - d e v i c e ( G ) . T h e greater p a r t o f the h y d r a u l i c system is placed i n the p u m p r o o m (see F i g ; 11). T h e general a r r a n g e m e n t o f t h a t r o o m is g i v e n i n F i g . 14. Six p u m p s are arranged f o r . T h e possibility o f a p p l y i n g an ali:ernating load w i t h a period o f a b o u t 7 seconds is p r o v i d e d . P r o v i s i o n -a l l y , o n l y t w o p u m p s -are i n s t -a l l e d g i v i n g -a p e r i o d o f about 1 m i n u t e f o r a l t e r n a t i n g loads. T h u s load cycles can be a p p l i e d w i t h the same p e r i o d as. i n r e a l i t y .
T h e t e s t i n g m a c h i n e , w h e n used s t a t i c a l l y , ha.9 f o u r ranges v i z . 5 00, 250, 100 and 50 tons; T h e e r r o r i n the m a c h i n e is smaller t h a n 1 % f o r a range f r o m . 10 % f u l l - l o a d t o f u l l - l o a d . W h e n used d y n a m i c a l l y the p e n d u l u m - m a n o m e t e r is s h u t o f f and 4 B o u r d o n manometers w i t h m a x i m u m - a n d m i n i m u m valves i n d i c a t e t h e n the t o p values o f the loading cycles.
T h e b u f f e r i n the high-pressure o i l system is p r o v i d e d b y t w o n i t r o g e n - a c c u m u l a t o r s placed i n the p u m p r o o m . A | l sorts o f s a f e t y devices are
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installed i n d i c a t i n g pressures, end o f stroke, m a x i m u m pressure etc. Signal lamps give all i n f o r m a t i o n w a n t e d on the c o n t r o l panel, w h i c h is b u i l t j u s t above the machine as indicated i n F i g . 2.
b. T h e 100 tons f a t i g u e t e s t i n g machine, w h i c h is
also a tensile and compression testing machine T h i s m a c h i n e i n d i c a t e d i n F i g . 1 as E is s h o w n i n F i g . 15. I t was m a n u f a c t u r e d b y A m s l e r & Co., S c h a f f h a u s e n and is equipped f o r tension, compression and b e n d i n g tests. I t is placed on a v i b r a t i o n -f r e e -f o u n d a t i o n . T h e p r i n c i p a l data o -f this testing machine are:
L o a d c a p a c i t y f r o m + 100 tons t o — 100 tons; range o f a l t e r n a t i n g load, 100 tons; m a x i m u m stroke, 6,3 m m load cycles per m i n u t e , 250 and 500; m a x . l e n g t h o f test piece 1000 m m
( 3 ' - 3 " ) ; range o f statical measurements 100, 50, 20 and 10 tons.
T h e statical measurements are made w i t h a p e n d u l u m - m a n o m e t e r . D y n a m i c measurements are made w i t h B o u r d o n manometers.
c. T h e 6 tons f a t i g u e testing machine
T h i s machine, i n d i c a t e d i n F i g . 1 as C is shown i n F i g . 16. I t is made b y Losenhausen, G e r m a n y and w i l l be used f o r m a k i n g fatigue-tests o n small structures i n steel and l i g h t - a l l o y s .
T h e p r i n c i p a l data are:
L o a d capacity f r o m -|- 6 tons t o — 6 tons; range o f a l t e r n a t i n g load, 6 tons; n u m b e r o f load cycles per m i n u t e , 1000, 1500, 2000 and 3000; m a x i m u m l e n g t h o f test-piece, 400 m m ( l ' - 4 " ) .
5. Conclnsion
T h e description o f this m o d e r n l a b o r a t o r y f o r research o n ships' structures as set u p at the U n i v e r s i t y o f T e c h n o l o g y i n D e l f t , is t h o u g h t to be o f general interest. I t is hoped t h a t m u c h i n -f o r m a t i o n w i l l be o b t a i n e d -f r o m this l a b o r a t o r y , w h i c h w i l l be o f use t o all concerned i n s h i p -b u i l d i n g .
